1. Field of the Invention
The present invention relates to processes for preparing aqueous dispersions of designated antimicrobial agents. These dispersions and various uses thereof are also claimed. The present dispersions are generally useful for inhibiting microbial growth in typical media where such microbial growth occurs.
More particularly, the present invention is concerned with processes for making aqueous dispersions of 2-(4-thiazolyl)-benzimidazole, alone or in combination with 1,2-dibromo-2,4-dicyanobutane. These processes rely on the use of xanthan gum to stabilize the dispersions. The present invention also relates to the novel dispersions described herein and to methods of inhibiting microbial growth comprising contacting said growth with an effective amount of the dispersions prepared by the processes herein disclosed.
2. Description of the Background Art
A number of important industries have experienced adverse effects from the activity of biological growth on the raw materials which they employ, in their process waters, on various components of their manufacturing processes, and in the finished products which they produce.
Such industries include, inter alia, the paint, wood, textile, cosmetic, leather, tobacco, fur, rope, paper, pulp, plastics, fuel, oil, rubber and machine industries. In these industries, therefore, it is generally desirable to utilize one or more biocides in an attempt to control microorganism populations. As used herein, the phrases "biocide", "antimicrobial" and "inhibiting microbial growth" describe the killing, inhibition or control of biological growth including but not limited to bacteria, algae and fungi such as yeast, mold and mildew.
Both 2-(4-thiazolyl)-benzimidazole (TBZ), also known as thiabendazole, and related compounds and l,2-dibromo-2,4-dicyanobutane (DBDCB), also known as 2-bromo-2-bromomethyl-glutaronitrile, and related compounds are known in the art as antimicrobial agents, both alone and in combination with other compounds. TBZ is commercially available as a dispersion from Calgon Corporation, Pittsburgh, Pa. and DBDCB is commercially available from Calgon Corporation in dry, organic solution and aqueous dispersion forms.
U.S. Pat. No. 4,830,657 describes a synergistic antimicrobial combination comprising DBDCB and 1,2-benzisothiazolin-3-one.
U.S. Pat. No. 4,442,122 describes the use of 1,2-dibromo-2-cyanoalkane compounds to inhibit microbial growth; this patent also discloses use of these compounds in conjunction with TBZ.
U.S. Pat. No. 4,496,581 describes the use of 1,2-dibromo-2-cyano-2-(heterocyclic) alkane compounds to inhibit microbial growth; this patent also discloses use of these compounds in conjunction with TBZ.
U.S. Pat. No. 5,034,405 describes admixtures of DBDCB, 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one as antimicrobial agents.
U.S. Pat. No. 3,370,957 describes TBZ and related compounds and their use in controlling fungal growth.
DBDCB and related compounds, and their use as antibacterial, antifungal and algicidal agents, are also disclosed in U.S. Pat. Nos. 3,833,731, 3,877,922, and 3,873,597. U.S. Pat. No. 3,833,731 further discloses the use of DBDCB in conjunction with TBZ as an antimicrobial agent; this patent, however, does not disclose an aqueous dispersion containing DBDCB and TBZ which utilizes xanthan gum as a stabilizer.
The xanthan gum based processes of the present invention, the resulting compositions and their use as antimicrobial agents are not known or suggested in the art.
One problem that is commonly experienced with commercially available TBZ dispersions is that they are not compatible with commercially available DBDCB dispersions. Furthermore, standard, commercial TBZ dispersions are often very difficult to meter and handle because of their viscosity. Thus, despite the commercial availability of TBZ and DBDCB dispersions, there remains a need for methods of producing stable aqueous dispersions containing either TBZ alone or TBZ in combination with DBDCB.
It is contemplated that the dispersions prepared by the processes of the present invention will have application in any industrial aqueous system in which inhibition of microbial growth is desired. Important applications are believed to include, inter alia, inhibiting the growth of bacteria in aqueous paints, adhesives, resins, drilling fluids, pigment dispersions, latex emulsions, metal-working fluids and joint cements; controlling mold and mildew growth on natural and synthetic fibers; preserving wood; preserving cutting oils; controlling slime-producing bacteria and fungi in pulp and paper mills and cooling towers; as a spray or dip treatment for textiles and leather to prevent mold growth; as a component of anti-fouling paints to prevent adherence of fouling organisms; protecting paint films, especially exterior paints, from attack by fungi which occurs during weathering of the paint film; protecting processing equipment from slime deposits during manufacture of cane and beet sugar; preventing microorganism buildup and deposits in air washer or scrubber systems and in industrial fresh water supply systems; controlling microorganism contamination and deposits in oil field drilling fluids and muds, and in secondary petroleum recovery processes; preventing bacterial and fungal growth in paper coating processes which might adversely affect the quality of the paper coating; controlling bacterial and fungal growth and deposits during the manufacture of various specialty boards, e.g. cardboard and particle board; preventing sap stain discoloration on freshly cut wood of various kinds; controlling bacterial and fungal growth in clay and pigment slurries of various types which are manufactured for later use in paper coating and paint manufacturing, for example, and which are susceptible to degradation by microorganisms during storage and transport; as a hard surface disinfectant to prevent growth of bacteria and fungi on walls, floors, etc.; and in swimming pools, ponds and cooling water systems to prevent algal growth.
An application for which the synergistic dispersion of DBDCB and TBZ as prepared by the processes of the present invention has been found especially useful is in the protection of paint films from attack by fungi. Paint film fungicides which can preserve paint films from the deleterious effects of fungal attack which occur during weathering of the paint film have long been sought. Few, however, have been found due to the stringent requirements for such a successful paint fungicide. Moreover, the ability to provide in-can preservative activity, as well as paint film protection, is also desirable. This additional characteristic is seldom seen in a paint film fungicide. A synergistic admixture of DBDCB and TBZ as prepared according to the methods of the present invention is particularly useful, therefore, in functioning as an all in one in-can preservative and mildewcide.
It is believed that the aqueous TBZ dispersions prepared by the methods of the present invention can be used in any application in which TBZ would be used, assuming that substantial problems with miscibility between the TBZ dispersion and the system being treated do not arise. Likewise, the aqueous dispersion containing blends of DBDCB and TBZ can be used in any application in which use of these two components together would be beneficial; this provides a further advantage in that it allows for the simultaneous feeding of both DBDCB and TBZ in one product at a predetermined, desired ratio. Because the aqueous dispersions prepared according to the processes of the present invention are in a form which is easy to meter and pump, it is anticipated that the improved handling properties of these aqueous dispersions will allow for their use in even more applications than TBZ alone, and TBZ in combination with DBDCB, are currently employed.